According to a current practice, the tobacco industry makes extensive use of a variety of flavoring active materials to improve the organoleptic properties of the different sorts of tobaccos it normally utilizes to manufacture a wide range of consumable articles. Tobacco aromatization has been carried out in the past according to several different techniques and methods, two methods though have acquired general acceptance: the soaking of tobacco in a solution, typically an aqueous one, of the flavor and the spraying of an aqueous or alcoholic solution of the flavor onto the tobacco.
The main drawback of these methods is that the active aromatic components of the flavor composition used, which generally consists in a variety of ingredients of different chemical constitution, possess in most of the cases a high vapor pressure already at room temperature and that consequently they tend to evaporate from the surface of the treated product shortly after the treatment.
In order to overcome this disadvantage, several techniques of flavor encapsulation have been suggested. U.S. Pat. No. 3,550,598 describes a process which consists in spraying the tobacco product with a suspension of hydrosoluble flavor entrapping capsules. This method has been applied in particular to the manufacture of reconstituted tobacco sheets using tobacco fines and dust accumulated in tobacco processing operations.
U.S. Pat. No. 3,623,489 describes a process for the aromatization of shredded tobacco which consists in the addition thereto of rupturable microcapsules incorporating a synthetic clove flavoring material. The capsules are of such a size as to create an audible crackling sound when burned liberating at the same time the active flavor volatile, generally eugenol. This patent suggests that the microcapsules can be manufactured according to any known current technique.
Other aromatization methods have been suggested in the past, none of them however has encountered sofar any major interest. In this respect, one may cite the addition of the flavorant to a polymeric element destined to be incorporated into a cigarette filter (U.S. Pat. No. 3,603,319) or the utilization of a cationic or anionic exchange resin having the property of being able to bind to certain molecules of basic or acid flavoring material (U.S. Pat. No. 3,280,823).
The prior art is rich in specific examples concerning the aromatization of foodstuffs by microencapsulation. Among the most recently published ones, attention is drawn to European Pat. No. 11 324, U.S. Pat. No. 4,339,422 and European Pat. No. 70 719. All these documents describe processes for the preparation of microcapsules by a technique known under the designation of "bed fluidization". More particularly, European Pat. No. 70 719 describes an encapsulation process for volatile liquids which consists in the agglomeration of the volatile liquid in a solution of a carrier material onto fluidized solid particles. The resulting solid capsules of substantially greater than those which can be made in small spray-drying towers entrap the active volatile liquids and can be utilized in aromatize consumable materials by direct addition thereto.
Bed fluidization is a technique which has encountered wide acceptability within the industry. This technique requires however a constant severe control of all the intervening physical parameters and cannot be applied to any and all materials. On the other hand, in many instances it has become apparent that the thus obtained solid particles containing the active flavor tend to mix in a non-uniform manner when added to the material to be flavored, a situation which may give rise to unhomogeneous aromatization.